UE-41286

Crash when using Mesh Reduction on ScotsPine_01 for LOD3

Crash when using Mesh Reduction on ScotsPine_01 for LOD3

A crash occurs when trying to use the Mesh Reduction tool for the ScotsPine_01 static mesh from the Open World Demo collection.

The assets from this project are usually very processor heavy due to the high resolution textures and number of triangles. Working with large numbers of these can affect performance so it would make sense to have more accurate and controlled LODs.

I think the user was originally attempting this with the asset as the transition from LOD2 to LOD3 was a mesh to billboard transition. The ultimate goal was to have a lower poly LOD3 without it being a billboard.

Steps to Reproduce

1. Open attached project (see comments for shareable link)
2. Open the ScotsPine_01 static mesh and set the Number of LODs to 3.0
3. Apply Changes.
4. Set the Number of LODs back to 4.0
5. Under LOD3 set the Percent Triangles in the Reduction Settings to 50.0
6. Apply Changes.

Outcome Crash occurs after applying changes and attempting to create a new LOD using the Percent Triangles.

Expected No crash and LOD3 now has have the number of Triangles as LOD2 which is where LOD3 was copied.